JAVA Level 10

1~5. 다음 코드에 대한 출력 결과를 쓰시오.

 

1.

public class Main {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Hello from thread"));
        thread.start();
    }
}

 

2.

public class Main {
    public static void main(String[] args) {
        Runnable task = () -> System.out.println("Running in a thread");
        Thread thread = new Thread(task);
        thread.start();
    }
}

 

3.

public class Main {
    public static void main(String[] args) {
        Counter counter = new Counter();
        Thread t1 = new Thread(counter::increment);
        Thread t2 = new Thread(counter::increment);
        t1.start();
        t2.start();
    }
}

class Counter {
    private int count = 0;

    public synchronized void increment() {
        count++;
        System.out.println(count);
    }
}

 

4.

public class Main {
    public static void main(String[] args) {
        Object lock = new Object();
        
        Thread t1 = new Thread(() -> {
            synchronized(lock) {
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 1 resumed");
            }
        });

        Thread t2 = new Thread(() -> {
            synchronized(lock) {
                lock.notify();
                System.out.println("Thread 2 completed");
            }
        });

        t1.start();
        t2.start();
    }
}

 

5.

public class Main {
    public static void main(String[] args) {
        Thread t1 = new Thread(new Task("Task 1"));
        Thread t2 = new Thread(new Task("Task 2"));
        t1.start();
        t2.start();
    }
}

class Task implements Runnable {
    private String name;

    public Task(String name) {
        this.name = name;
    }

    @Override
    public void run() {
        for (int i = 0; i < 3; i++) {
            System.out.println(name + ": " + i);
        }
    }
}

 

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정답
(드래그 시 정답이 보입니다.)

1. Hello from thread
2. Running in a thread
3. 1

2

4. Thread 2 completed
Thread 1 resumed

5. Task 1: 0
Task 1: 1
Task 1: 2
Task 2: 0
Task 2: 1
Task 2: 2